Method of patterning a device

ABSTRACT

A photopolymer layer is formed on an organic device substrate and exposed to patterned radiation. The photopolymer layer includes a photopolymer comprising at least a first repeating unit having an acid-catalyzed, solubility-altering reactive group, wherein the total fluorine content of the photopolymer is less than 30% by weight. The pattern exposed photopolymer is contacted with a developing agent, such as a developing solution, to remove unexposed photopolymer, thereby forming a developed structure having a first pattern of exposed photopolymer covering the substrate and a complementary second pattern of uncovered substrate corresponding to the unexposed photopolymer. The developing agent comprises at least 50% by volume of a hydrofluoroether developing solvent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of PCT/US2012/065007, filedNov. 14, 2012, which claims benefit of U.S. Ser. No. 61/559,168, filedNov. 14, 2011 and which applications are incorporated herein byreference. To the extent appropriate, a claim of priority is made toeach of the above disclosed applications.

BACKGROUND

1. Field of the Invention

The present invention relates to acid-catalyzed switchable photopolymersthat are processed at least in part using a fluorinated solvent, whereinthe photopolymers have reduced or substantially no fluorine content.Such solvents and photopolymers are particularly useful for patterningorganic electronic and biological materials.

2. Discussion of Related Art

Organic electronic devices can offer significant performance and priceadvantages relative to conventional inorganic-based devices. As such,there has been much commercial interest in the use of organic materialsin electronic device fabrication. For example, organic materials such asconductive polymers and organic semiconductors can be used tomanufacture devices that have reduced weight and drastically greatermechanical flexibility compared to conventional electronic devices basedon metals and silicon. Further, devices based on organic materials arelikely to be significantly less damaging to the environment than devicesmade with inorganic materials, since organic materials do not requiretoxic metals and can ideally be fabricated using relatively benignsolvents and methods of manufacture. Thus, in light of these superiorweight and mechanical properties, and particularly in light of thelowered environmental impact in fabrication and additionally indisposal, electronic devices based on organic materials have thepotential to be less expensive than devices based on conventionalinorganic materials.

Fabrication of electronic devices, whether from organic or inorganicmaterials, requires the creation on an industrial scale of preciselydefined patterns of the organic or inorganic active materials in thesedevices, often at a microscopic level. Most commonly, this isaccomplished by “photolithography,” in which a light-sensitive“photoresist” film that has been deposited on a substrate is exposed topatterned light. Although this can be done in numerous ways, typically amicroscopic pattern of light and shadow created by shining a lightthrough a photographic mask is used to expose the photoresist film,thereby changing the chemical properties of the portions of thephotoresist that have been exposed to light. In a “positive”photoresist, the portions of the photoresist that are exposed to lightbecome soluble in the “developer” solution that is then applied to theexposed photoresist, and the light-exposed portions of the photoresistare washed away (“developed”) by the developer solvent to leave apattern of unexposed photoresist and newly exposed underlying substrate.A “negative” photoresist is treated as for a positive photoresist;however, in a negative photoresist, it is the unexposed rather than theexposed portions of the photoresist that are washed away by thedeveloping step.

In a standard process, the photoresist material is laying on top of anactive material layer that is to be patterned. Once the development hastaken place, the underlying layer is etched using either a liquidetchant or a reactive ion plasma (RIE) with the appropriate etchchemistry. In either case, the photoresist layer blocks the etching ofactive material directly beneath it. Once the etching is complete, theresist is typically stripped away, leaving the pattern of activematerial on the substrate.

Alternatively, the photoresist can be used with a so-called “liftoff”technique. In this case, the resist is processed on a substrate beforethe active material layer is deposited. After the photoresist pattern isformed, the active material is deposited on both the substrate and thephotoresist. In an additional “lift-off” or “stripping” step, remainingphotoresist along with an overlying layer of active material is removedvia the appropriate solvent to leave the desired patterned activematerial.

Although the use of photoresists is routine in traditional electronicdevices based on inorganic materials, photolithography has beendifficult to achieve for devices using organic materials, therebyhindering the development of devices based on these materials.Specifically, organic materials are much less resistant to the solventsthat are used for conventional photolithography, as well as to theintense light sources that are sometimes used in these processes, withthe result that conventional lithographic solvents and processes tend todegrade organic electronics. Although there have been various attemptsto overcome these problems, e.g., by ink-jet printing or shadow maskdeposition, these alternative methods do not produce the same results aswould be obtained with successful photolithography. Specifically,neither ink-jet printing nor shadow mask deposition can achieve the finepattern resolutions that can be obtained by conventional lithography,with ink-jet printing limited to resolutions of approximately 10-20 μmand shadow mask deposition to resolutions of about 25-30 μm.

US 2011/0159252 discloses a useful method for patterning organicelectronic materials by an “orthogonal” process that uses fluorinatedsolvents and photoresists having substantial amounts of fluorination.The fluorinated solvents have very low interaction with organicelectronic materials. WO 2012/148884 discloses additional fluorinatedmaterial sets for orthogonal processing.

Although these disclosures demonstrate good progress, the disclosedsystems have yet to be commercially adopted. Further improvements inorthogonal, photopolymer systems are needed with respect to performanceand cost.

SUMMARY

In accordance with the present disclosure a method of patterning anorganic electronic device using a photopolymer comprises: forming aphotopolymer layer on an organic electronic device substrate by coatinga composition comprising a photopolymer and a hydrofluoroether coatingsolvent, the photopolymer comprising at least a first repeating unithaving an acid-catalyzed, solubility-altering reactive group, whereinthe total fluorine content of the photopolymer is less than 30% byweight; exposing the photopolymer layer to patterned radiation to forman exposed photopolymer layer; and contacting the exposed photopolymerlayer with a developing solution to remove unexposed photopolymer,thereby forming a developed structure having a first pattern of exposedphotopolymer covering the substrate and a complementary second patternof uncovered substrate corresponding to the unexposed photopolymer, thedeveloping solution comprising at least 50% by volume of ahydrofluoroether developing solvent.

In an embodiment, the reduced fluorine content of the photopolymerresults in lower manufacturing cost due to reduced use of fluorinatedfunctional groups, which are often expensive. In an embodiment,developing and stripping solutions comprise environmentally safesolvents, despite the low fluorine content of the photopolymer, and theorthogonal behavior with respect to sensitive active organic materialsis maintained. In an embodiment, good contrast can be achieved (e.g.,contrast of at least 1.5) using environmentally safe solvents within areasonable development time, despite the low fluorine content of thephotopolymer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a representative plot of normalized thickness vs. log(exposure) used to determine photopolymer contrast;

FIG. 2 is a flow chart depicting the steps in an embodiment of thepresent invention;

FIG. 3A-3F is a series of cross-sectional views depicting various stagesin the formation of a patterned active organic material structureaccording to an embodiment of the present invention;

FIG. 4A-4D is a series of cross-sectional views depicting various stagesin the formation of a patterned active organic material structureaccording to another embodiment of the present invention; and

FIG. 5 shows photographic images of poly-TBMA photopolymer patternsafter UV exposure and development on a Si substrate (left) and on aPEDOT:PSS-coated PET substrate (right).

DETAILED DESCRIPTION

It is to be understood that the attached drawings are for purposes ofillustrating the concepts of the invention and may not be to scale.

An embodiment of the present invention is directed to patterning organicdevices, e.g., multilayer organic electronic devices, organic opticaldevices, medical devices, biological devices and the like. In anembodiment, the photopolymer is used as a photoresist and removed(stripped) after use. Alternatively, the photopolymer may remain in adevice structure to provide another function, e.g., as a barrier layeror a dielectric material.

Certain embodiments disclosed in the present disclosure are particularlysuited to the patterning of solvent-sensitive, active organic materials.Examples of active organic materials include, but are not limited to,organic electronic materials, such as organic semiconductors, organicconductors (e.g. PEDOT:PSS), OLED (organic light-emitting diode)materials and organic photovoltaic materials, organic optical materials,medical materials and biological materials. Many of these materials areeasily damaged when contacted with organic or aqueous solutions used inconventional photolithographic processes. Active organic materials areoften coated to form a layer that may be patterned. For some activeorganic materials, such coating can be done from a solution usingconventional methods. Alternatively, some active organic materials arepreferentially coated by vapor deposition, for example, by sublimationfrom a heated organic material source at reduced pressure.Solvent-sensitive, active organic materials can also include compositesof organics and inorganics. For example, the composite may includeinorganic semiconductor nanoparticles (quantum dots). Such nanoparticlesmay have organic ligands or be dispersed in an organic matrix.

An embodiment of the present invention is based in part on theobservation that, surprisingly, certain photopolymers having relativelylow fluorination (less than 30% by weight) can still be coated anddeveloped using hydrofluoroether solvents. Hydrofluoroether solventsrepresent a class of “orthogonal” solvents that have relatively lowinteraction with sensitive organic materials. An orthogonal solvent isone having low interaction with other device material layers that arenot intended to be dissolved or otherwise damaged during processing withthe solvent. This can be tested by, for example, immersion of a devicecomprising the material layer of interest into the solvent prior tooperation. The solvent is orthogonal if there is no serious reduction inthe functioning of the device. Hydrofluoroethers (HFEs) are highlyenvironmentally friendly, “green” solvents. HFEs, including segregatedHFEs, are preferred solvents because they are non-flammable, have zeroozone-depletion potential, lower global warming potential than someother halogenated solvents and typically show very low toxicity tohumans.

Examples of readily available HFEs and isomeric mixtures of HFEsinclude, but are not limited to, an isomeric mixture of methylnonafluorobutyl ether and methyl nonafluoroisobutyl ether (HFE-7100), anisomeric mixture of ethyl nonafluorobutyl ether and ethylnonafluoroisobutyl ether (HFE-7200 aka Novec™ 7200), 3-ethoxy-I,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane (HFE-7500aka Novec™ 7500),1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-pentane (HFE7600 aka Novec™ 7600), 1-methoxyheptafluoropropane (HFE-7000),1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethylpentane(HFE-7300 aka Novec™ 7300), 1,3-(1,1,2,2-tetrafluoroethoxy)benzene(HFE-978m), 1,2-(1,1,2,2-tetrafluoroethoxy)ethane (HFE-578E),1,1,2,2-tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether (HFE-6512),1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE-347E),1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE-458E), and1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorooctane-propyl ether (TE6O-C3). Inan embodiment, preferred HFE solvents for developing photopolymershaving less than 30% by weight fluorine include HFE-7100, HFE-7200,HFE-7600 and HFE-6512 and close isomers.

The developing solution comprises at least 50% by volume of ahydrofluoroether or a mixture of hydrofluoroethers. In an embodiment,the developing solution comprises at least 90% by volume of ahydrofluoroether or a mixture of hydrofluoroethers. In an embodiment,the developing solution comprises at least 95% by volume of ahydrofluoroether or a mixture of hydrofluoroethers. In an embodiment,the substantially all (>99% by volume) of the developing solution iscomprised of a hydrofluoroether or a mixture of hydrofluoroethers.

In some embodiments, minor amounts of a non-fluorinated solvent may beadded to the developing solution. Such non-fluorinated solvents includechlorinated solvents, polar solvents, alcohols and other protic organicsolvents, and substituted or unsubstituted hydrocarbons and aromatichydrocarbons, so long as they are miscible with the fluorinated solventin the amounts desired for the developing solution and maintainorthogonal behavior with respect to active organic materials.

The optional stripping solution typically comprises a hydrofluoroether,a polar organic solvent or both. In an embodiment, the polar organicsolvent is a protic organic solvent, also referred to herein simply as aprotic solvent. When the fluorine content of the photopolymer is lessthan about 15%, particularly less than about 10% by weight, it ispreferred that the stripping solution comprise a protic solvent, e.g.,as the sole solvent or as a co-solvent with one or morehydrofluoroethers. In an embodiment, the stripping solution may comprisea hydrofluoroether solvent (or a mixture of hydrofluoroether solvents)but no protic solvent, preferably when the fluorine content of thephotopolymer is more than about 10%, particularly more than about 15%,by weight, and preferably when the polymer includes a branching unit.Preferred protic solvents include hydroxyl-containing non-aromaticorganic compounds such as alcohols, e.g., methanol, ethanol, isopropylalcohol, butanol, pentane, and hexanol and their derivatives andisomers. In an embodiment, the stripping solution comprises a proticsolvent with no hydrofluoroether. Protic solvents typically have asignificant cost advantage over hydrofluoroethers, and thus the overallmanufacturing cost can be substantially reduced by replacing thehydrofluoroether stripping solvent with the protic solvent. This may beused so long as any the protic solvent retains its orthogonal behaviorwith respect to any active organic materials that may be present.However, it has been found that even small amounts of protic solvents ina hydrofluoroether solvents make effective stripping solutions, but havea much reduced impact on sensitive organic materials. In an embodiment,the stripping solution is a mixture of a hydrofluoroether strippingsolvent and a protic solvent, e.g., an alcohol. When using suchmixtures, the protic solvent may be provided in a range of 0.1% to 50%by volume, or alternatively, 0.5% to 20% by volume, or alternatively 1%to 5% by volume. The lower amount of protic solvent increases the rangeof compatibility with various sensitive organic materials. The higheramount of protic solvent may result in more significant manufacturingcosts. In an embodiment, the stripping solution comprises a mixture of aprotic solvent with a hydrofluoroether solvent, and the hydrofluoroethersolvent is the same as the hydrofluoroether used in the developingsolution. This can greatly simplify recycling of developing andstripping solutions, thereby resulting in further manufacturing costsavings.

The photopolymer of the present disclosure is one that has at least afirst repeating unit having an acid-catalyzed, solubility-alteringreactive group. The total fluorine content of the photopolymer is lessthan 30% by weight. In an embodiment, the photopolymer has substantiallyno fluorination (less than 1% fluorine by weight). In an embodiment, thetotal fluorine content of the photopolymer is in a range of 0 to 15% byweight, or alternatively, in a range of 1 to 15%. In an embodiment, thetotal fluorine content of the photopolymer is in a range of 0 to 10% byweight, or alternatively, in a range of 1 to 10%. In an embodiment, aphotopolymer having a small amount of fluorine (e.g., at least 1% byweight) can significantly improve stripping rate relative to a polymerhaving no fluorine. In an embodiment wherein the fluorine content isabove 0%, the first repeating unit may include one or more fluorineatoms.

In an embodiment, the photopolymer further includes (in addition to thesolubility-altering reactive group) a repeating unit having afluorine-containing group. In an embodiment, the photopolymer furtherincludes (in addition to the solubility-altering reactive group) arepeating unit having a sensitizing dye. In an embodiment thephotopolymer further includes (in addition to the solubility-alteringreactive group) one or more branching units. In a preferred embodiment,the acid-catalyzed, solubility-altering reactive group is anacid-forming precursor group or an alcohol-forming precursor group. Theterms “photopolymer”, “polymer” and “copolymer” include oligomers inaddition to higher MW polymers. In an embodiment, the MW of thephotopolymer is at least 2500 daltons, or in another embodiment at least5000 daltons, or in another embodiment, at least 10,000 daltons. Acopolymer is suitably a random copolymer, but other copolymer types canbe used, e.g., block copolymers, alternating copolymers, graftcopolymers and periodic copolymers. The term “repeating unit” is usedbroadly herein and simply means that there is at least one unit,typically more than one unit, on a polymer chain. The term is notintended to convey that there is necessarily any particular order orstructure with respect to the other repeating units unless specifiedotherwise. When a repeating unit represents a low mole % of the combinedrepeating units, there may be only one unit on a polymer chain.

A coatable photopolymer solution may include the photopolymer material,a photo-acid generator compound (PAG) and a coating solvent thatcomprises at least 50% of a fluorinated solvent, preferably ahydrofluoroether, and may optionally further include one or moreadditional components such as a stabilizer, a light sensitizer, a lightfilter, an acid scavenger (quencher) or a coating aid. Common quenchersinclude, but are not limited to, basic nitrogen-containing compoundssuch as tertiary amines. A layer comprising the photopolymer materialshould be sensitive to radiation, e.g., UV or visible light, e-beam,X-ray and the like, so that the solubility properties of the exposedareas are selectively altered to enable development of an image. In apreferred embodiment, the radiation is UV or visible light.

The photopolymer may be produced, for example, by co-polymerizingsuitable monomers containing the desired repeating units along with apolymerizable group. The polymerizable group may, for example, bepolymerized by step-growth polymerization using appropriate functionalgroups or by a chain polymerization such as radical polymerization. Somenon-limiting examples of useful radical polymerizable groups includeacrylates (e.g. acrylate, methacrylate, cyanoacrylate and the like),acrylamides, vinylenes (e.g., styrenes), vinyl ethers and vinylacetates. Alternatively, the photopolymer may be produced byfunctionalizing preformed polymers to attach desired repeating units.

In an embodiment, the solubility-altering reactive group is anacid-forming precursor group that is acid-catalyzed (chemicallyamplified). Upon exposure to light, the acid-forming precursor groupgenerates a polymer-bound acid group, e.g., a carboxylic or sulfonicacid. This can drastically change its solubility relative to theunexposed regions thereby allowing development of an image with theappropriate solvent. In an embodiment, the developing solution comprisesa hydrofluoroether developing solvent that selectively dissolvesunexposed areas.

A chemically amplified acid-forming precursor group typically requiresaddition of a photo-acid generator (PAG) to the photopolymercomposition, e.g., as a small molecule additive to the solution. The PAGmay function by directly absorbing radiation (e.g. UV light) to causedecomposition of the PAG and release an acid. Alternatively, asensitizing dye may be added to the composition whereby the sensitizingdye absorbs radiation and forms an excited state capable of reactingwith a PAG to generate an acid. The sensitizing dye may be added as asmall molecule, or alternatively, may be attached to, or otherwiseincorporated as part of, the photopolymer as another repeating unit, asdiscussed below. In an embodiment, the sensitizing dye (either smallmolecule or attached) is fluorinated. In an embodiment, the sensitizingdye may be provided in a range of 0.5 to 10% by weight relative to thetotal copolymer weight. The photochemically generated acid catalyzes thede-protection of acid-labile protecting groups of the acid-formingprecursor. In certain cases, such de-protection may occur at roomtemperature, but commonly, an exposed chemically amplified photopolymeris heated for a short time (“post exposure bake”) to more fully activatede-protection “switching”. In some embodiments, chemically amplifiedphotopolymers can be desirable since they enable the exposing step to beperformed through the application of relatively low energy UV lightexposure (e.g., less than 500 mJ/cm² or in some embodiments under 100mJ/cm²). This is advantageous since some active organic materials usefulin applications to which the present disclosure pertains may decomposein the presence of too much UV light, and therefore, reduction of theenergy during this step permits the photopolymer to be exposed withoutcausing significant photolytic damage to underlying active organiclayers. Also, reduced light exposure times improve the manufacturingthroughput of the desired devices.

Examples of acid-forming precursor groups that yield a carboxylic acidinclude, but are not limited to: A) esters capable of forming, orrearranging to, a tertiary cation, e.g., t-butyl ester, t-amyl ester,2-methyl-2-adamantyl ester, 1-ethylcyclopentyl ester, and1-ethylcyclohexyl ester; B) esters of lactone, e.g.,γ-butyrolactone-3-yl, γ-butyrolactone-2-yl, mavalonic lactone,3-methyl-γ-butyrolactone-3-yl, 3-tetrahydrofuranyl, and 3-oxocyclohexyl;C) acetal esters, e.g., 2-tetrahydropyranyl, 2-tetrahydrofuranyl, and2,3-propylenecarbonate-1-yl; D) beta-cyclic ketone esters, E)alpha-cyclic ether esters and F) MEEMA (methoxy ethoxy ethylmethacrylate) and other esters which are easily hydrolyzable because ofanchimeric assistance. In an embodiment, a polymerizable monomercomprises an acrylate-based polymerizable group and a tertiary alkylester acid-forming precursor group, e.g., t-butyl methacrylate (“TBMA”)or 1-ethylcyclopentyl methacrylate (“ECPMA”).

In an embodiment, the total fluorine content of the photopolymer is in arange of 0% to 15% by weight and the acid-forming precursor groupincludes a non-cyclic, tertiary alkyl ester moiety, wherein thenon-cyclic, tertiary alkyl comprises 10 or fewer carbon atoms, oralternatively, 6 or fewer carbon atoms. In an embodiment, theacid-forming precursor group includes a cyclic alkyl ester moiety andthe photopolymer has a fluorine content of at least 10% but less than30% by weight.

In an embodiment, the solubility-altering reactive group is anhydroxyl-forming precursor group (also referred to herein as an“alcohol-forming precursor group”). The hydroxyl-forming precursorincludes an acid-labile protecting group and the photopolymercomposition typically includes a PAG compound and operates as a“chemically amplified” type of system. Upon exposure to light, the PAGgenerates an acid (either directly or via a sensitizing dye as describedabove), which in turn, catalyzes the de-protection of thehydroxyl-forming precursor group, thereby forming a polymer-boundalcohol (hydroxyl group). This significantly changes its solubilityrelative to the unexposed regions thereby allowing development of animage with the appropriate fluorinated solvent. In an embodiment, thedeveloping solution includes a fluorinated solvent that selectivelydissolves unexposed areas.

In an embodiment, the hydroxyl-forming precursor has a structureaccording to formula (1):

wherein R₅ is a carbon atom that forms part of the first repeating unit(or first polymerizable monomer), and R₁₀ is an acid-labile protectinggroup. Non-limiting examples of useful acid-labile protecting groupsinclude those of formula (AL-1), acetal groups of the formula (AL-2),tertiary alkyl groups of the formula (AL-3) and silane groups of theformula (AL-4).

In formula (AL-1), R₁₁ is a monovalent hydrocarbon group, typically astraight, branched or cyclic alkyl group, of 1 to 20 carbon atoms thatmay optionally be substituted with groups that a skilled worker wouldreadily contemplate would not adversely affect the performance of theprecursor. In an embodiment, R₁₁ may be a tertiary alkyl group. Somerepresentative examples of formula (AL-1) include:

In formula (AL-2), R₁₄ is a monovalent hydrocarbon group, typically astraight, branched or cyclic alkyl group, of 1 to 20 carbon atoms thatmay optionally be substituted. R₁₂ and R₁₃ are independently selectedhydrogen or a monovalent hydrocarbon group, typically a straight,branched or cyclic alkyl group, of 1 to 20 carbon atoms that mayoptionally be substituted. Some representative examples of formula(AL-2) include:

In formula (AL-3), R₁₅, R₁₆, and R₁₇ represent an independently selecteda monovalent hydrocarbon group, typically a straight, branched or cyclicalkyl group, of 1 to 20 carbon atoms that may optionally be substituted.Some representative examples of formula (AL-3) include:

In formula (AL-4), R₁₈, R₁₉ and R₂₀ are independently selectedhydrocarbon groups, typically a straight, branched or cyclic alkylgroup, of 1 to 20 carbon atoms that may optionally be substituted.

The descriptions of the above acid-labile protecting groups for formulae(AL-2), (AL-3) and (AL-4) have been described in the context ofhydroxyl-forming precursors. These same acid-labile protecting groups,when attached instead to a carboxylate group, may also be used to makesome of the acid-forming precursor groups described earlier.

In an embodiment, a photopolymer comprising a solubility-alteringreactive group having a non-aromatic cyclic substituent has at least10%, by weight of fluorine, and further includes one or more branchingunits. In an embodiment, a photopolymer comprising a solubility-alteringreactive group having a non-aromatic oxygen-containing heterocyclicsubstituent has at least 5%, preferably at least 10% by weight offluorine, and further includes one or more branching units.

The PAG should have some solubility in the coating solvent anddeveloper. The amount of PAG required depends upon the particularsystem, but generally, will be in a range of about 0.1 to 6% by weightrelative to the photopolymer. In an embodiment, the presence of asensitizing dye may substantially reduce the amount of PAG requiredrelative to a composition that does not include a sensitizing dye. In anembodiment, the amount of PAG is in a range of 0.1 to 3% relative to thephotopolymer. PAGS that are fluorinated or non-ionic or both areparticularly useful. Some useful examples of PAG compounds include2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene(ONPF) and2-[2,2,3,3,4,4,4-heptafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene(HNBF). Other non-ionic PAGS include: norbornene-based non-ionic PAGssuch as N-hydroxy-5-norbornene-2,3-dicarboximideperfluorooctanesulfonate, N-hydroxy-5-norbornene-2,3-dicarboximideperfluorobutanesulfonate, and N-hydroxy-5-norbornene-2,3-dicarboximidetrifluoromethanesulfonate; and naphthalene-based non-ionic PAGs such asN-hydroxynaphthalimide perfluorooctanesulfonate, N-hydroxynaphthalimideperfluorobutanesulfonate and N-hydroxynaphthalimidetrifluoromethanesulfonate.

Some additional classes of PAGs include: triarylsulfoniumperfluoroalkanesulfonates, such as triphenylsulfoniumperfluorooctanesulfonate, triphenylsulfonium perfluorobutanesulfonateand triphenylsulfonium trifluoromethanesulfonate; triarylsulfoniumhexafluorophosphates (or hexafluoroantimonates), such astriphenylsulfonium hexafluorophosphate and triphenylsulfoniumhexafluoroantimonate; triaryliodonium perfluoroalkanesulfonates, such asdiphenyliodonium perfluorooctanesulfonate, diphenyliodoniumperfluorobutanesulfonate, diphenyliodonium trifluoromethanesulfonate,di-(4-tert-butyl)phenyliodonium, perfluorooctanesulfonate,di-(4-tert-butyl)phenyliodonium perfluorobutanesulfonate, anddi-(4-tert-butyl)phenyliodonium trifluoromethanesulfonate; andtriaryliodonium hexafluorophosphates (or hexafluoroantimonates) such asdiphenyliodonium hexafluorophosphate, diphenyliodoniumhexafluoroantimonate, di-(4-tert-butyl)phenyliodoniumhexafluorophosphate, and di-(4-tert-butyl)phenyliodoniumhexafluoroantimonate. Suitable PAGs are not limited to thosespecifically mentioned above. Combinations of two or more PAGs may beused as well.

In an embodiment, the photopolymer further comprises (in addition to thefirst repeating unit) a repeating unit having a fluorine-containinggroup. The fluorine containing group is preferably a fluorine-containingalkyl or aryl group that may optionally be further substituted withchemical moieties other than fluorine, e.g., chlorine, a cyano group, ora substituted or unsubstituted alkyl, alkoxy, alkylthio, aryl, aryloxy,amino, alkanoate, benzoate, alkyl ester, aryl ester, alkanone,sulfonamide or monovalent heterocyclic group, or any other substituentthat a skilled worker would readily contemplate that would not adverselyaffect the performance of the photopolymer. In a preferred embodiment,the fluorine-containing group is an alkyl group having at least 5fluorine atoms, or alternatively, at least 10 fluorine atoms. In anembodiment, the alkyl group is a hydrofluorocarbon or hydrofluoroetherhaving at least as many fluorine atoms as carbon atoms. In anembodiment, the fluorine-containing group is perfluorinated alkyl or a1H,1H,2H,2H-perfluorinated alkyl having at least 4 carbon atoms, forexample, 1H,1H,2H,2H-perfluorooctyl (i.e., 2-perfluorohexyl ethyl).Throughout this disclosure, unless otherwise specified, any use of theterm alkyl includes straight-chain, branched and cyclo alkyls. In anembodiment, the repeating unit having a fluorine-containing group doesnot contain protic or charged substituents, such as hydroxy, carboxylicacid, sulfonic acid, quaternized amine or the like. A non-limitingexample of a polymerizable monomer having a fluorine containing group is1H,1H,2H,2H-perfluorooctyl methacrylate (“FOMA”).

In an embodiment, the photopolymer further comprises (in addition to thefirst repeating unit) a repeating unit having a sensitizing dye. Thepresence of a sensitizing dye can reduce the amount of radiationexposure required for imaging the photopolymer. In an embodiment using arepeating unit having as sensitizing dye, the photopolymer has at least1%, preferably at least 5% fluorine by weight. A fluorinated polymer canhelp solubilize an attached sensitizing dye in a fluorinated solvent,thereby enabling the use of a sensitizing dye that might otherwise havepoor solubility.

In an embodiment, a repeating unit having a sensitizing dye has nofluorine atoms and is provided in a weight range of 1 to 10% relative tothe copolymer, alternatively in a weight range of 1 to 6% relative tothe copolymer, or in another embodiment, in a weight range of 1 to 4%relative to the copolymer.

In an embodiment, a repeating unit having a sensitizing dye is alsopartially fluorinated. The fluorine atoms can be included as part of apolymerizable group or as part of the sensitizing dye. Fluorine can beattached to an alkyl, aryl or heteroaryl moiety. In an embodiment, arepeating unit comprising a sensitizing dye and which is partiallyfluorinated is provided in a weight range of 1 to 20% relative to thephotopolymer, alternatively in a weight range of 2 to 15% relative tothe copolymer.

Some non-limiting examples of useful sensitizing dye classes includecyanine dyes, rhodamine compounds, dialkylaminobenezes, diaryl ketones(e.g., benzophenones), arylalkyl ketones (e.g., acetophenones),chromanones, xanthones, thioxanthones, benzothiazoles, benzoxazoles,benzimidazoles, pyrimidines, quinolines, coumarins, psoralens,pyrromethenes, naphthalenes, anthracenes, tetracenes, pyrelenes, andpyrenes.

In an embodiment, the photopolymer further comprises (in addition to thefirst repeating unit) a repeating unit having “dry-etch-resistant”group. It is common in photolithography to etch patterns into layersusing a “dry etchant” with the patterned photopolymer acting as an etchbarrier. Herein, the term “dry etchant” is used broadly and refers toany useful gaseous material possessing energy sufficient to etch(remove) a target material. Dry etching includes, but is not limited to,glow discharge methods (e.g., sputter etching and reactive ion etching),ion beam etching (e.g., ion milling, reactive ion beam etching, ion beamassisted chemical etching) and other “beam” methods (e.g., ECR etchingand downstream etching), all of which are methods known in the art. Somecommon dry etchants include oxygen plasma, argon plasma, UV/ozone, CF₄and SF₆, and various combinations.

It can be advantageous, therefore, for the photopolymer to havereasonable resistance to the dry etch to ensure good pattern transfer tothe underlying layer. The photopolymer may optionally comprise arepeating unit having a dry-etch-resistant group, e.g., a cyclic alkylsuch as adamantyl or isobornyl, or a group that includes at least onedry-etch-resistant atom having an atomic weight of at least 24. In anembodiment, the dry-etch-resistant atom is Si, Ti, Ge, Al, Zr, or Sn.The dry-etch-resistant group may optionally be formed from apolymerizable monomer, e.g., one that has a cyclic alkyl, anorganosilane, a siloxane, silazane or metalloxane group. In a preferredembodiment, the dry-etch-resistant group includes a silane or siloxanegroup.

In an embodiment, the photopolymer may further comprise (in addition tothe first repeating unit) a branching unit to form a branched polymer.The term “branched polymer” refers to a polymer chain having at leastone branching unit that forms one or more branch points connecting threeor more chain segments. In some embodiments, branched photopolymers haveimproved solubility. It has been found that branching makes availablemore variations in repeating units that may otherwise have impracticallylow solubility in fluorinated solvents when provided as straight-chaintype polymers. A branched copolymer of the present disclosure may be abrush/comb type, a star type, a hyperbranched type, dendrimer type orany other known in the art. The branched copolymer may simply have threechain segments or many more. A generic structure is shown below asbranched polymer (A):

wherein Ch1 is a first chain segment, Ch2 is a second chain segment, Ch3is a third chain segment and BU is a branching unit. In an embodiment,the branching unit may be conveniently defined as a single atom capableof bonding to at least three polymer chain segments, e.g., a carbon,nitrogen, silicon or aluminum atom. In an embodiment, the branching unitmay be conveniently defined as chemical compound, typically a compoundhaving multiple polymerizable groups or other functional groups capableof forming branch points.

In an embodiment, the branching unit is provided by a branching monomerhaving at least two polymerizable sites capable of being copolymerizedwith other monomers, such as a monomer comprising a solubility-alteringreactive group. Some representative examples of branching monomersinclude: aliphatic or alicyclic divinyl hydrocarbons such as isoprene,butadiene, 3-methyl-1,2-butadiene, 2,3-dimethyl-1,3-butadiene,1,2-polybutadiene, pentadiene, hexadiene, octadiene, cyclopentadiene,cyclohexadiene, cyclooctadiene, norbornadiene, and the like; aromaticdivinyl hydrocarbons such as divinylbenzene, divinyltoluene,divinylxylene, trivinylbenzene, divinylbiphenyl, divinylnaphthalene,divinylfluorene, divinylcarbazole, divinylpyridine, and the like;diivinyl and diallyl esters such as divinyl adipate, divinyl maleate,divinyl phthalate, divinyl isophthalate, divinyl itaconate,vinyl(meth)acrylate, diallyl maleate, diallyl phthalate, diallylisophthalate, diallyl adipate, allyl(meth)acrylate, and the like;divinyl and diallyl ethers such as diallyl ether, diallyloxyethane,triallyloxyethane, tetraallyloxyethane, tetraallyloxypropane,tetraallyloxybutane, tetramethallyloxyethan; divinyl ether, diethyleneglycol divinyl ether, triethylene glycol divinyl ether, and the like;divinyl ketones; diallyl ketones; fluorine-containing divinyl compoundssuch as 1,4-divinylperfluorobutane, 1,6-divinylperfluorohexane,1,8-divinylperfluorooctane, and the like; nitrogen-containing divinylcompounds such as diallylamine, diallylisocyanurate, diallylcyanurate,methylenebis(meth)acrylamide, bismaleimide, and the like;silicon-containing divinyl compound such as dimethyldivinylsilane,divinylmethylphenylsilane, diphenyldivinylsilane,1,3-divinyl-1,1,3,3-tetramethyldisilazane,1,3-divinyl-1,1,3,3-tetraphenyldisilazane, diethoxyvinylsilane, and thelike.

In a preferred embodiment, the branching monomer having at least twopolymerizable sites are based on (meth)acrylic acid esters such asethylene glycol di(meth)acrylate (EGD(M)A), triethylene glycoldi(meth)acrylate, propylene glycol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, trimethylolpropane tri(meth)acrylate,ditrimethylolpropane tetra(meth)acrylate, glycerol tri(meth)acrylate,pentaerythritol tetra(meth)acrylate, alkoxytitanium tri(meth)acrylate,1,6-hexanediol di(meth)acrylate, 2-methyl-1,8-octanedioldi(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanedioldi(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, dioxaneglycol di(meth)acrylate,2-hydroxy-1-acryloyloxy-3-methacryloyloxypropane,2-hydroxy-1,3-di(meth)acryloyloxypropane,9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene, undecylenoxyethyleneglycol di(meth)acrylate, bis[4-(meth)acryloylthiophenyl]sulfide,bis[2-(meth)acryloylthioethyl]sulfide, 1,3-adamantanedioldi(meth)acrylate, 1,3-adamantanedimethanol di(meth)acrylate, and thelike.

A combination of multiple branching monomers or branching units havingdifferent chemical structures may be used. In an embodiment, the mole %of branching units relative to the total of all copolymer units is in arange of 1-10%, or alternatively, in a range of 2-6%. Methods forpreparing branched polymers by radical polymerization can be found, forexample, in U.S. Pat. No. 6,646,068 and US Publication No. 2012/0135206,the contents of which are incorporated by reference. In an embodiment,chain transfer agents are used in conjunction with a radicalpolymerization initiator to control branching.

Non-limiting examples of useful chain transfer agents include thiolssuch as alkyl mercaptans (e.g., dodecyl mercaptan), alkylkthioglycolates (e.g., 2-ethyl hexyl thioglycolate), polyfunctionalthiols, and brominated compounds such as carbon tetrabromide. In thepolymerization reaction, a thiol type chain transfer agent may terminatepolymerization of a chain segment by addition of a thiol radical to forma sulfur-containing terminal group, e.g., a thioether. In the case ofcarbon tetrabromide, a chain segment-terminating bromine or abromine-containing group may be formed. In an embodiment, chain transferagent is provided into the reaction vessel in a mol ratio relative tothe branching monomer in a range of 0.05 to 10, or in another embodimentin a range of 0.1 to 5, or in another embodiment 0.5 to 2.

In an embodiment, the photopolymer may further include (in addition tothe first repeating unit) a repeating unit comprising an alkyl oraromatic group that is neither fluorinated nor an acid-catalyzed,solubility-altering reactive group. It may be used to adjust variousproperties of the photopolymer such as its solubility, reactivity,coatability, Tg or other property.

The photopolymer may include various combinations of repeating unitsdescribed above.

A photopolymer composition of the present disclosure may be applied to asubstrate (sometimes referred to herein as an organic device substrate)using any method suitable for depositing a photosensitive liquidmaterial. For example, the composition may be applied by spin coating,curtain coating, bead coating, bar coating, spray coating, dip coating,gravure coating, ink jet, flexography or the like. The composition maybe applied to form a uniform film or a patterned layer of unexposedphotopolymer. Alternatively, the photopolymer can be applied to thesubstrate by transferring a preformed photopolymer layer (optionallypatterned) from a carrier sheet, for example, by lamination transferusing heat, pressure or both. In such an embodiment, the substrate orthe preformed photopolymer layer may optionally have coated thereon anadhesion promoting layer.

The contrast of the present photopolymer system can be an importantperformance factor. Higher contrast is typically preferred, as itgenerally results in straighter sidewalls for imaged areas and overallbetter discrimination between imaging light and stray light for improvedfeature resolution.

To study contrast, the following method was generally used which can bemodified as needed by one skilled in the art. A subject photopolymer wasspin coated onto a silicon wafer and soft-baked on a hot plate for 1 minat 90° C. The film thickness was generally in a range of about 1 to 1.5μm. An optical 22-step tablet (˜0.15 density units per step) was laid ontop of the wafer and the resist was exposed to 365 nm radiation using a16 W filtered black light lamp. The maximum exposure dose was typicallyabout 175 mJ/cm². The wafer was post-exposure baked (PEB) on a hot platefor 1 min at 90° C. to activate the switching reaction. The filmthickness was then immediately measured in 24 areas (steps). In additionto the 22 areas of the step tablet, the maximum exposure dose wasmeasured just outside of the step tablet area (point 1) as well as aminimum exposure dose area (covered by a metal disc) that received noexposure (point 24).

Five minutes after the PEB, the wafer was contacted with ˜10 mL of adeveloper solution by forming a “puddle” over the wafer and spin-driedafter the target time was reached. The time of each puddle and number ofpuddles depended on the system. After each puddle, the film thicknesseswere measured in the same 24 areas. Film thicknesses after each puddlewere normalized to the starting thickness and plotted versus logExposure (log(E)) to create a set of contrast curves. The contrastbetween each point was calculated using equation 1:

Contrast=[Δnormalized thickness]/[Δ log(E)]  (Eq. 1)

The highest calculated contrast (the “maximum contrast”) for each curvewas determined. FIG. 1 shows an example graph of normalized thicknessvs. log(E)—for clarity, only the first 16 points are shown. Otherparameters can also be determined as desired such as “0.5 speed point”(exposure dose at normalized film thickness=0.5), “Emax erosion”(normalized thickness loss of the maximum exposure point 1), “time toclear” (time it takes for the minimum exposure to be fully removed), and“time to strip” (time it takes for maximum exposure to be fullyremoved). In an embodiment, the photopolymer has a contrast of at least1.5, preferably at least 1.9.

In an embodiment, the present invention can be used to form organicdevices having a layer of sensitive, active organic material (seeabove). Such devices may include electronic devices such as TFTs, touchscreens, OLED lighting and displays, e-readers, LCD displays, solarcells, sensors and bioelectronics devices. These devices are oftenmultilayer structures having numerous other layers such as dielectriclayers, optical layers, conductors and a support. Devices may includenon-electronic devices such as optical, medical, and biological deviceshaving some patterned active organic material, but that do not requirean electrical conductor or semiconductor to operate (e.g., lenses, colorfilter arrays, down- or up-conversion filters, medical/biological teststrips and the like). The organic device substrate onto which thephotopolymer is provided may include a single layer of a supportmaterial or may include a multilayer structure having a support andnumerous additional layers. The substrate surface is not necessarilyplanar. The substrate and support are optionally flexible. Supportmaterials include, but are not limited to, plastics, metals, glasses,ceramics, composites and fabrics.

A flow diagram for an embodiment of the present invention is shown inFIG. 2, and includes the step 2 of forming a photopolymer layer on asubstrate. This can be accomplished using methods previously described.

In step 4, the photopolymer layer is exposed to patterned radiation,e.g. UV light, to form an exposed photopolymer layer having a pattern ofexposed photopolymer and a complementary pattern of unexposedphotopolymer. The term “radiation” refers to any radiation to which thephotopolymer is sensitive and can form areas of differentialdevelopability due to some chemical or physical change caused by theradiation exposure. Non-limiting examples of radiation include UV,visible and IR light, e-beams and X-rays. Commonly, the radiation isfrom UV or visible light. Patterned radiation can be produced by manymethods, for example, by directing exposing light through a photomaskand onto the photopolymer layer. Photomasks are widely used inphotolithography and often include a patterned layer of chrome thatblocks light. The photomask may be in direct contact or in proximity.When using a proximity exposure, it is preferred that the light has ahigh degree of collimation. Alternatively, the patterned light can beproduced by a projection exposure device. In addition, the patternedlight can be from a laser source that is selectively directed to certainportions of the photopolymer layer. After exposure and optional postexposure bake, at least some of the solubility-altering reactive groups(e.g. acid- or alcohol-forming precursor groups) in the exposed patternhave reacted to form a reacted group (e.g. an acid or alcohol group).

In step 6, a developed structure is formed that includes a first patternof photopolymer. This can be done by contacting the exposed photopolymerlayer to a developing solution comprising a hydrofluoroether developingsolvent. During development, the complementary pattern of unexposedphotopolymer is removed (negative working photopolymer). Developmentleaves behind a developed structure having a first pattern ofphotopolymer that covers the substrate and a complementary secondpattern of uncovered substrate corresponding to the removed portion ofphotopolymer. By uncovered substrate, it is meant that the surface ofthe substrate is substantially exposed or revealed to a degree that itcan be subjected to further treatments—a small amount of residualphotopolymer may be present in some embodiments. Contacting the exposedphotopolymer layer can be accomplished by immersion into the developingsolution or by applying the developing solution in some way, e.g., byspin coating or spray coating. The contacting can be performed multipletimes if necessary.

In step 8, a treated structure is formed by treating the developedstructure in some way. In an embodiment, the treating includes achemical or physical etch of the second pattern of uncovered substrate.In this case, the first pattern of photopolymer acts as an etch barrier.In another embodiment, the treating includes chemically modifying thesurface of the second pattern of uncovered substrate or the firstpattern of photopolymer. In another embodiment, the treating includesdoping, oxidizing, or reducing the second pattern of uncoveredsubstrate, e.g., to modify its conductivity. In yet another embodiment,the treating includes coating the developed structure with, for example,an active organic material that is deposited both on the surface of thefirst pattern of photopolymer and on the second pattern of uncoveredsubstrate. In any of the above embodiments, the substrate may optionallyinclude an active organic material layer such that the uncoveredsubstrate is the surface of that active organic material layer.

In step 10, the first pattern of photopolymer is optionally removed fromthe treated structure using a stripping solution. In embodiments whereinthe surface of the first pattern of photopolymer is covered with anotherlayer of material, e.g., an active organic material layer, that portionis also removed. This is sometimes referred to as a “lift off” process.

Turning now to FIG. 3, there is a series of cross-sectional viewsdepicting the formation of a patterned active organic material structureat various stages according to an embodiment of the present invention.In FIG. 3A, a substrate 20 includes a layer of active organic material24 provided on a support 22. In FIG. 3B, a photopolymer layer 26 isformed on the substrate 20 and in contact with the layer of activeorganic material 24. Next, as shown in FIG. 3C, photopolymer layer 26 isexposed to patterned light by providing a photomask 30 between thephotopolymer layer 26 and a source of collimated light 28. The exposedphotopolymer layer 32 includes a pattern of exposed photopolymer areas34 and complementary pattern of unexposed photopolymer areas 36. Thestructure is then developed in a developing solution comprising ahydrofluoroether developing solvent. As illustrated in FIG. 3D theunexposed areas 36 of the photopolymer are selectively dissolved to forma developed structure 38 having a first pattern of photopolymer 40covering the substrate, and a complementary second pattern of uncoveredsubstrate 42, in this case the layer of active organic material 24,corresponding to the removed portion of photopolymer. Turning now toFIG. 3E, a treated structure 44 is formed by subjecting the developedstructure 38 to a chemical or physical etch that selectively removesactive organic material from the second pattern of uncovered substrate,thereby forming a patterned layer of active organic material 46corresponding to the first pattern. By corresponding, it is meant thatthe patterned layer of active organic material 46 substantiallyresembles that of the first pattern of photopolymer 40, but the twopatterns are not necessarily identical. For example, the etching mightalso etch the sidewalls of the patterned layer of active organicmaterial, thereby making the dimensions slightly smaller than the firstpattern. Conversely, etching kinetics or diffusion might be such thatthe dimensions of the patterned layer of active organic material areslightly larger than the first pattern. Further, the patterned layer ofactive organic material might not have vertical sidewalls as shown.Rather than rectangular, its cross section could resemble a trapezoid,an inverted trapezoid (undercut), or some other shape, e.g., one havingcurved sidewalls. Referring to FIG. 3F, treated structure 44 iscontacted with a stripping solution that removes the first pattern ofphotopolymer 40, thereby forming patterned active organic materialstructure 48 having the (now bare) patterned layer of active organicmaterial 46. Patterned active organic material structure 48 mayoptionally be subjected to additional steps, if necessary, to form afunctional device such as an organic TFT array, an OLED display, ane-reader, a solar cell, a touch screen, a bioelectronic device, amedical device or the like.

In a related embodiment to that shown in FIG. 3, the active organicmaterial 24 is a conductive polymer and the developed structure 38 istreated with a chemical oxidant to form a treated structure. In thisembodiment, the conductive polymer is not removed, but rather, itsconductivity has been substantially reduced or deactivated in a patterncorresponding to the second. Examples of suitable chemical oxidants aredisclosed, e.g., in US 2013/0295354.

FIG. 4 shows a series of cross-sectional views depicting the formationof a patterned active organic material structure at various stagesaccording to another embodiment of the present invention. In FIG. 4A, aphotopolymer layer 126 is formed on substrate 120. This structure isthen exposed and developed as described above to form developedstructure 138, as shown in FIG. 4B. Developed structure 138 has a firstpattern of photopolymer 140 covering the substrate, and a complementarysecond pattern of uncovered substrate 142 corresponding to a removedportion of photopolymer. Turning now to FIG. 4C, a treated structure 144is formed by depositing a layer of active organic material 145 over boththe first pattern of photopolymer and the second pattern of uncoveredsubstrate. In FIG. 4D, the treated structure 144 is then contacted witha stripping solution that removes the first pattern of photopolymer andthe active organic material deposited over the first pattern ofphotopolymer, thereby forming patterned active organic materialstructure 148 having a patterned layer of active organic material 146corresponding to the second pattern. By corresponding, it is meant thatthe patterned layer of active organic material 146 substantiallyresembles that of the second pattern of uncovered substrate 142, but thetwo patterns are not necessarily identical. Patterned active organicmaterial structure 148 may optionally be subjected to additional steps,if necessary, to form a functional device such as an organic TFT array,an OLED display, an e-reader, a solar cell, a bioelectronic device orthe like.

EXAMPLES

In the examples below, most of the HFE solvents were purchased from 3Munder their Novec™ brand. For convenience, the solvents are simplyreferred to by their HFE number. HFE-6512 was purchased from TopFluorochem Co, LTD.

Synthesis Example 1 (Poly-TBMA)

To a 250 mL jacketed four-necked flask equipped with a teflon-bladestirrer, a reflux condenser with a mineral oil bubbler outlet,sub-surface nitrogen sparge tube, and a thermometer was charged 28.4 g(˜32.5 m L, 0.2 mol.) tert-butyl methacrylate (TBMA), 87.2 g (˜56.5 mL)HFE-7600 and 0.723 g (4.38 mmol.) AIBN [2.5 wt % initiator level]. Theagitator motor was programmed for 200 rpm stirring. The sparge tube wasadjusted so it is below the surface of the solution and nitrogen wasbubbled subsurface for 1 hour. During the sparge, the constanttemperature bath (CTB) connected to the jacket of the reaction flask waspreheated to 76° C. with flow to the flask turned off. When the nitrogensparge was complete the nitrogen flow was reduced so that a slightpositive flow was maintained throughout the reaction. The valves to theCTB were opened to the reaction flask. The reaction was stirred for 20hours at 200 rpm with 76° C. fluid circulating through the flask jacket.The reaction mixture was cooled to ambient temperature and diluted to6.8 wt % by the addition of 302 g of HFE-7600. The poly-TBMA hassubstantially no fluorine content, but was surprisingly soluble in thishydrofluoroether solvent.

A 42 g sample of this solution was removed and the solvent was removedin vacuo to provide a solid sample of dry polymer suitable foranalytical testing. Size Exclusion Chromatography showed Mn=16200,Mw=58700, Mw/Mn=3.624, and the Tg was determined to be 110.6° C. A PAGcompound can be added to the desired amount to make the photosensitivecomposition. In this particular example, 0.254 g of CGI 1907 (“ONPF” akaCiba 1907) from BASF was added as the PAG to the remaining solution.

Various polymers and copolymers using different monomers can be preparedby one skilled in the art by appropriate modification of the methoddescribed above. HFE-6512 is another useful solvent for preparation andof these polymers.

Example 1

A composition comprising 8% by weight solution of poly-TBMA in HFE-7600from Synthesis Example 1 (0% fluorine by weight) was spin coated onto aSi wafer at 1000 rpm to form a photopolymer layer approximately 1.5 μmthick. The film was post apply baked on a hot plate at 90° C. for 60seconds to remove excess solvent. The bake temperature or time can beadjusted to control the free volume of the polymer film to control suchaspects as PAG diffusion or airborne amine penetration that can cause“amine poisoning” of the surface, causing less acid reaction near thesurface compared with the bulk of the film. Temperature may also belowered to work with a particularly temperature sensitive active organicmaterial that may be underneath the photopolymer layer or with atemperature sensitive support, such as PET. An oven bake may also beused instead of the hot plate bake.

The photopolymer layer was exposed to UV radiation, activating thephoto-acid through light absorption by the PAG. In the presentembodiment, Ciba 1907 PAG from BASF was used, being sensitive at i-line(365 nm) and shorter wavelengths, but another PAG with differentwavelength sensitivities could be substituted, as long as the PAG issoluble in HFE-7600 casting solvent. The UV light was filtered through aphotomask in order to expose the resist in particular places to formpatterns of exposed and unexposed regions in the photopolymer layer.Typical exposure doses ranged from 20-880 mJ/cm2 at 365 nm.

The resist was then subjected to a post exposure bake (PEB) on a hotplate at 90° C. for 60 seconds to cause the photo-generated acid toreact with, and de-protect, the TBMA units, turning them intomethacrylic acid (MAA) units on the same chain. A longer bake time orhigher bake temperature will result in more de-protection, comparable toa higher UV exposure dose.

The resist film was then developed with HFE-7600 in the presentembodiment, although another hydrofluoroether solvent that solvates theresist film can be used instead (e.g., HFE-6512). The developer removesthe unexposed areas that have not been deprotected, resulting in anegative tone pattern on the substrate. The areas that have beendeprotected, or partially deprotected, become less soluble to thedeveloper and remain. FIG. 5 shows the results of this exposure anddevelopment process on a poly-TBMA resist with Ciba 1907 PAG from BASF.The image on the left shows features down to 1 μm lines/spaces formed ona silicon substrate using an i-line ASML stepper exposure tool. Theimage on the right shows 60 μm lines and 25 μm spaces, and was obtainedusing a contact aligner exposure tool with the poly-TBMA provided on topof a flexible PET substrate coated with the conducting polymerPEDOT:PSS. Following development, the imaged poly-TBMA structures canoptionally be stripped by contact with a stripping solution comprising aprotic solvent such as IPA.

Example 2 Dissolution Rate Measurements

A series of photopolymer solutions were prepared using HFE-7600 ascoating solvent, CGI 1907 as PAG (2.0% by wt relative to polymer wt),and photopolymers prepared by copolymerizing TBMA with various amountsof FOMA, the mol ratios for which are shown in Table 1. The dissolutionrate for unexposed polymers coated on Si wafers were measured byinterferometry using a Filmetrics F20 Thin-Film Analyzer using eitherHFE-7600 or HFE-6512 as the hydrofluoroether developing solvent. Thedissolution was usually directly proportional to contact time indicatingthat mass transport was not rate-limiting.

TABLE 1 TBMA/FOMA Dissolution rate (nm/sec) type mol ratio (%) % F byweight HFE-6512 HFE-7600 Comp  50/50 42.8 >1000 770 Inv 93/7 10.6 50 18Inv 95/5 7.9 39 13 Inv 97/3 4.9 35 12 Inv 99/1 1.7 52 19 Inv 100/0  0 4615

The solubility of copolymers of TBMA at low FOMA levels was surprising.One can see a downward trend in dissolution rates as FOMA level getslower, but the dissolution rates are perfectly acceptable for practicaldevelopment times. Even more unexpected was the observation that at 0and 1 mol % FOMA, the solubility trend partially reversed, being higherthan 3 and 5% FOMA. Although poly-TBMA (0 mol % FOMA) provides thelargest raw material cost advantage relative to 50% FOMA copolymers, the1% FOMA provides a useful increase in development rate and is stillsignificantly less expensive than 50% FOMA.

Example 3

Contrast curves (see above for procedure) were measured for the 0, 1 and7 mol % FOMA polymers from Example 2 using HFE-7600 or HFE-6512 as thehydrofluoroether developing solvent. The photopolymer layer were eachabout 1.0 μm thick. Various parameters were determined as reported inTable 2. In this example, the maximum exposure dose was about 175mJ/cm².

TABLE 2 Stripping Max Contrast solvent Est. time TBMA/FOMA Developing (@dev (+5% to strip mol ratio (%) solvent time, sec) vol. IPA) Emax (sec)100/0  7600  3.6 (150) 7600 100 100/0  6512 4.9 (60) 6512 180 3.9 (90)99/1 7600 1.7 (90) 7600 110  3.5 (150) 99/1 6512 3.4 (30) 6512 45 3.8(45) 93/7 7600 3.0 (90) 7600 110  3.5 (150) 93/7 6512 3.7 (60) 6512 853.0 (90)

Table 2 shows that good contrasts were achieved in both developingsolvents, but slightly higher contrasts were observed in HFE-6512 andthey were obtained at shorter development times, consistent withdissolution rate data from Table 1. The maximum exposure step (Emax) ofall samples stripped in an adequate time period with only 5% by volumeof IPA added to the HFE solvent. Typically, higher IPA (protic solvent)will result in faster stripping. A small amount of FOMA (even just 1mole %) in the polymer significantly reduces time to strip inHFE-6512/IPA stripping solution.

Example 4

ECPMA (1-ethylcyclopentyl methacrylate) is a polymerizable monomerhaving an acid-forming precursor group, specifically, a cyclic tertiaryalkyl ester. Attempts to synthesize a pure poly-ECPMA polymer inHFE-7600 at high concentration were unsuccessful (significantprecipitation was observed). Although there may be some solubility ofpoly-ECPMA in HFE-7600, in some embodiments, it is preferred to coatfrom a hydrofluoroether solvent and solubility issues may limit filmthickness. Nevertheless, it was surprisingly found that adding a lowlevel fluorination to the polymer, preferably with some amount ofbranching, can provide a very useful photopolymer that may be preparedin HFE-7600. For example, a branched polymer was prepared in HFE-7600comprising a copolymer of FOMA, ECPMA, and EGDMA (ethylene glycoldimethylacrylate) in mole ratios of 20, 76 and 4, respectively. Thephotopolymer had 21.2% by weight of fluorine relative to the polymerweight. CGI 1907 was added to the solution at 2% by weight relative tothe polymer. The dissolution rate of a layer of this photopolymer inHFE-7600 was determined to be 210 nm/sec. A contrast curve was measuredas described above using HFE-7600 as the developer except the maximumexposure=325 mJ/cm², and the post exposure bake was 3 min at 90° C. Thephotopolymer had a maximum contrast of 3.3 at just 30 s of development.There was thickness non-uniformity in some of the steps, but it wasclearly suitable for use in many photolithographic applications. Themaximum exposure step (Emax) stripped completely in less than 15 secondsusing HFE-7600 having 20% by volume IPA.

Example 5

THPOEMA (2-[(2-tetrahydropyranyl)oxy]ethyl methacrylate) is apolymerizable monomer having an alcohol-forming precursor group. LikeExample 4, attempts to synthesize a pure poly-THPOEMA polymer inHFE-7600 at high concentration were unsuccessful (significantprecipitation was observed). Although there may be some solubility ofpoly-THPOEMA in HFE-7600, in some embodiments, it is preferred to coatfrom a hydrofluoroether solvent and solubility issues may limit filmthickness. Nevertheless, it was surprisingly found that adding a lowlevel of fluorination to the polymer, preferably with some amount ofbranching, can provide a very useful photopolymer that may be preparedin HFE-7600. For example, a branched polymer was prepared in HFE-7600comprising a copolymer of FOMA, THPOEMA, and EGDMA in mole ratios of 10,86 and 4, respectively. The photopolymer had 10.5% by weight of fluorinerelative to the polymer weight. CGI 1907 was added to the solution at 2%by weight relative to the polymer. The dissolution rate of a layer ofthis photopolymer in HFE-7600 was determined to be at least 210 nm/sec.A second branched THPOEMA polymer was prepared comprising a copolymer ofFOMA, THPOEMA, and EGDMA in mole ratios of 20, 76 and 4, respectively.The photopolymer had 19.2% by weight of fluorine relative to the polymerweight. CGI 1907 was added to the solution at 2% by weight relative tothe polymer. The dissolution rate of a layer of this photopolymer inHFE-7600 was determined to be about 560 nm/sec (very fast). There wassignificant thickness non-uniformity for these particular polymers forreasons unknown, which made obtaining reliable contrast curves difficultdue to uncertainties in obtaining film thickness measurements. Still,the films appear to have high contrast and are believed to be suitablefor use in many photolithographic applications. The maximum exposurestep (325 mJ/cm² with post exposure bake of 3 min at 90° C.) strippedcompletely in less than 15 seconds using HFE-7600 having 20% by volumeIPA for the first THPOEMA polymer. The second THPOEMA polymer strippedin less than 5 sec.

Example 6

A photopolymer was prepared comprising a copolymer of FOMA, TBMA andAMMA (9-anthrylmethyl methacrylate, a sensitizing dye) in mole ratios of23/75/2 respectively. The photopolymer had 26.8% fluorine by weightrelative to the photopolymer. CGI 1907 was added to the solution at 2%by weight relative to the polymer. The dissolution rate of a layer ofthis photopolymer in HFE-7600 was determined to be about 100 nm/sec. Acontrast curve was measured as described above using HFE-7600 as thedeveloper (maximum exposure=175 mJ/cm², and the post exposure bake was 1min at 90° C.). The photopolymer had a maximum contrast of 2.9 at 30 sof development and 3.6 at 60 s of development. Relative to the samplesfrom Example 2, this photopolymer was more sensitive by about an orderof magnitude. The “0.5 speed points” at 30 s and 60 s development timeswere 1.5 and 2.0 mJ/cm², respectively. By way of example, the 93/7TBMA/FOMA “0.5 speed point” was about 36 mJ/cm² at its 90 s developmenttime in HFE-7600. In some embodiments, high photosensitivity is desiredin order to reduce overall exposure of the device to radiation. Themaximum exposure step (Emax) stripped completely in about 30 secondsusing HFE-7600 having 20% by volume IPA. It is noted that the maximumexposure was far higher than needed given the speed point. Thus, it islikely that a more appropriate exposure could be stripped in even lesstime or that lower IPA could be used.

Example 7

A branched photopolymer was prepared comprising a copolymer of FOMA,TBMA, AMMA and EGDMA in mole ratios of 23/75/2/3 respectively. Thephotopolymer had 26.6% fluorine by weight relative to the photopolymer.CGI 1907 was added to the solution at 2% by weight relative to thepolymer. The dissolution rate of a layer of this photopolymer inHFE-7600 was determined to be about 280 nm/sec. A contrast curve wasmeasured as described above using HFE-7600 as the developer (maximumexposure=175 mJ/cm², and the post exposure bake was 1 min at 90° C.). InHFE-7600, however, both exposed and unexposed features are removed. Thatis, HFE-7600 is an effective stripping agent without any protic solventadded with Emax stripped in about 100 sec.

A second contrast curve was measured using HFE-7200 as the developingagent. The dissolution rate of a layer of this photopolymer in HFE-7200was determined to be about 42 nm/sec. The photopolymer had a maximumcontrast of 1.6 at 30 s of development and 2.2 at 60 s of development.There was a small amount of dissolution of the Emax even in HFE-7200developing solution, but even at 60 s of development, >85% of the Emaxthickness was retained. Since no protic solvents are required (HFE-7600can be used as sole stripping solvent), this photopolymer is suitablefor use with a broad range of active organic materials. The reduced FOMA(fluorine %) makes this photopolymer more cost effective than some priorart orthogonal photoresist systems.

Example 8 PEDOT Stability with Various Treatments

The robustness of a conductive polymer (PEDOT:PSS, Aldrich, 3-4% inwater, high-conductivity grade) to various materials and methods of thepresent disclosure was tested as follows. A 1×1 inch glass substrate wasprovided with three parallel stripes of silver separated by about 6 mm.A film of PEDOT:PSS was applied by spin coating at 1000 rpm and thendried at 90° C. for 25 min. The resistance of the PEDOT:PSS film wasmeasured by contacting probes of an ohmmeter to the first and secondsilver lines before and after various treatments. One can mask off aportion of the silver lines prior to PEDOT coating or simply push theprobes through the PEDOT to make contact with the silver lines.Resistance measurements using the probes contacted to PEDOT directly(without silver contacts) were unreliable and typically very high due tohigh contact resistance. Results are shown in Table 3.

TABLE 3 Treatment Resistance (ohms) None (start) 26 1 min HFE-7600puddle, spin dry 26 1 min HFE-6512 puddle, spin dry 26 1 min HFE-7200puddle, spin dry 26 1 min IPA puddle, spin dry 26 Coat poly-TBMA (0% F)from Ex. 2; 26 bake 1.5 min at 90° C. (no light exposure); develop with2-45 sec puddles HFE-7600 Coat poly-TBMA (0% F) from Ex. 2; 26 bake 1.5min at 90° C.; expose 365 nm UV 260 mJ/cm², bake 1.5 min at 90° C; strip2-45 sec puddles HFE-7600 w/20% vol IPA

It is readily apparent that the materials and methods described aboveare fully compatible with PEDOT:PSS conductive polymer and nodegradation in conductivity was observed. A photolithographic patterningmethod using conventional photoresists have been disclosed in the priorart. However, standard developing and stripping agents are disclosed ashaving a negative impact on the PEDOT conductivity. See AGFA publication“Orgacon™ Conductive Transparent Films Application Sheet—PatterningOrgacon™ film by means of UV lithography” revised 05/2001. Thus, theprior art system is less robust and requires tighter process control.

Example 9 PEDOT Patterning

A PEDOT sample was prepared as described in Example 8. The resistance ofthe PEDOT between the first and second silver stripes was found to be40Ω, and similarly, the resistance of the PEDOT between the second andthird silver stripes was found also to be 40Ω. Poly-TBMA (0% F, 2% CGI1907 PAG) was spin coated from HFE-7600 coating solvent to provide ˜1 μmfilm and baked on a hot plate at 90° C. for 1 min. The film was exposedto 365 nm UV light to provide a total dose of ˜260 mJ/cm², then baked ona hot plate for 90° C. for 1 min. During the exposure, light was maskedin a 2 mm wide strip between, and parallel to, the first and secondsilver stripes. The film was developed in HFE-7600 for 150 sec therebyremoving unexposed photopolymer in the 2 mm wide strip. The developedstructure was treated by immersion for 5 min in a 5% by weight aqueoussolution of sodium diisocyanurate to deactivate conductivity of thePEDOT layer in the 2 mm wide developed area. The treated structure waswashed in tap water and then DI water for 1 min. The photopolymer wasthen stripped by contact with IPA for 60 sec. The resistance of thePEDOT between the first and second silver stripes was now too high tomeasure (no conductivity), whereas the resistance between the second andthird silver stripes was found to be 39Ω. Thus, the photopolymer actedas an effective photolithographic barrier to the sodium diisocyanurateand the processing solvents had no detrimental impact on the PEDOTconductivity.

Prior disclosures regarding orthogonal photoresists direct the skilledworker to use photopolymers having a fluorine content of at least 30% byweight. As described above, it has been found that photopolymers havinglower levels of fluorine, or even no fluorine, can be surprisinglyeffective. In certain embodiments, the low fluorine systems of thepresent disclosure can result in lower cost photopolymers, lower costphotoprocessing chemistry, improved recyclability (reduced cost andenvironmental impact), or combinations thereof, while maintainingorthogonal behavior with respect to sensitive active organic materials,and providing good film contrast in acceptable processing cycle times.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations, combinations, and modifications can be effected by a personof ordinary skill in the art within the spirit and scope of theinvention.

LIST OF REFERENCE NUMBERS USED IN THE DRAWINGS

-   2 form photopolymer layer on substrate step-   4 form exposed photopolymer layer step-   6 form developed structure step-   8 form treated structure step-   10 remove first pattern of photopolymer step-   20 substrate-   22 support-   24 layer of active organic material-   26 photopolymer layer-   28 light-   30 photomask-   32 exposed photopolymer layer-   34 exposed photopolymer areas-   36 unexposed photopolymer areas-   38 developed structure-   40 first pattern of photopolymer-   42 second pattern of uncovered substrate-   44 treated structure-   46 patterned layer of active organic material-   48 patterned active organic material structure-   120 substrate-   126 photopolymer layer-   138 developed structure-   140 first pattern of photopolymer-   142 second pattern of uncovered substrate-   144 treated structure-   145 layer of active organic material-   146 patterned layer of active organic material-   148 patterned active organic material structure

1. A method of patterning an organic device using a photopolymer,comprising: forming a photopolymer layer on an organic device substrate,the photopolymer layer including a photopolymer comprising at least afirst repeating unit having an acid-catalyzed, solubility-alteringreactive group, wherein the total fluorine content of the photopolymeris less than 30% by weight; exposing the photopolymer layer to patternedradiation to form an exposed photopolymer layer; and contacting theexposed photopolymer layer with a developing agent to remove unexposedphotopolymer, thereby forming a developed structure having a firstpattern of exposed photopolymer covering the substrate and acomplementary second pattern of uncovered substrate corresponding to theunexposed photopolymer, the developing agent comprising at least 50% byvolume of a hydrofluoroether developing solvent.
 2. The method of claim1 further comprising: treating the developed structure to form a treatedstructure; and contacting the treated structure with a stripping agentto remove the first pattern of exposed photopolymer.
 3. The method ofclaim 2 wherein the organic device substrate includes a layer of aconductive polymer and the complementary pattern of uncovered substratecomprises uncovered conductive polymer, and wherein the treatingincludes a plasma etch or a chemical deactivation of the uncoveredconductive polymer.
 4. The method of claim 2 wherein the stripping agentcomprises a hydrofluoroether stripping solvent or a protic solvent orboth.
 5. The method of claim 4 wherein the stripping agent comprises atleast 0.5% by volume of the protic solvent.
 6. The method of claim 5wherein the stripping agent comprises at least 50% by volume of thehydrofluoroether stripping solvent.
 7. The method of claim 6 wherein thehydrofluoroether stripping solvent is the same as the hydrofluoroetherdeveloping solvent.
 8. The method of claim 4 wherein the protic solventis an alcohol.
 9. The method of claim 1 wherein the total fluorinecontent of the photopolymer is in a range of 0% to 15% by weight. 10.The method of claim 9 wherein the total fluorine content of thephotopolymer is in a range of 1% to 15% by weight.
 11. The method ofclaim 9 wherein the solubility-altering reactive group is anacid-forming precursor group and includes a non-cyclic tertiary alkylester moiety, the non-cyclic tertiary alkyl comprising ten or fewercarbon atoms.
 12. The method of claim 11 wherein the non-cyclic tertiaryalkyl is t-butyl.
 13. The method of claim 1 wherein the photopolymerfurther includes a second repeating unit having a fluorine-containinggroup.
 14. The method of claim 13 wherein the photopolymer furtherincludes one or more branching units.
 15. The method of claim 13 whereinthe solubility-altering reactive group is an acid-forming precursorgroup or an alcohol-forming precursor group.
 16. The method of claim 13wherein the photopolymer further includes a third repeating unitcomprising a sensitizing dye.
 17. The method of claim 1 wherein thephotopolymer layer further comprises a non-ionic photo-acid generatorcompound.
 18. The method of claim 1 wherein the hydrofluoroetherdeveloping solvent is selected from the group consisting of an isomericmixture of methyl nonafluorobutyl ether and methyl nonafluoroisobutylether, an isomeric mixture of ethyl nonafluorobutyl ether and ethylnonafluoroisobutyl ether,3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane,1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-pentane,1-methoxyheptafluoropropane,1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane,1,3-(1,1,2,2-tetrafluoroethoxy)benzene,1,2-(1,1,2,2-tetrafluoroethoxy)ethane,1,1,2,2-tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether,1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether,1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorooctane-propyl ether.
 19. Themethod of claim 1 wherein the layer of photopolymer is provided bycoating a composition comprising the photopolymer and a hydrofluoroethercoating solvent.
 20. The method of claim 1 wherein the total fluorinecontent of the photopolymer is less than 1% by weight.